package BC117_小乐乐走台阶;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();

        int result = fun(n);
        System.out.println(result);
    }

    private static int fun(int n) {
        if (n == 0 || n == 1){
            return 1;
        }else {
            return fun(n - 1) + fun(n - 2);
        }
    }
}
